SPL and system curiosity

[simonwest]

Just something I'd like to ask and see what peoples opinions would be on the following.... (I've not mentioned the actual companies name / the actual product name deliberately!

 

Recently I went to see a very well known band at Manchester Apollo as a punter (the land of the punter still bewilders me, as one thought he'd try and smack my missus for simply standing where she was.. he was so drunk and stoned he didn't see myself and two other beefy guys stood next to her ready to kill him...but thats another story).

 

At this point bare in mind that the audio company responsible for the supply and the touring engineers are all 'professional' with years of experience etc etc.

 

The dates on their tour include venues like Apollo, Leeds Uni, and other Carling venues like Brixton... none exactly HUGE venues.

 

So I ask:

 

1. What would you consider to be an appropriate system design for these venues? I personally would have placed in XLC127+ with infills and flown xsubs. Stage is approx 12m wide.

 

'The companies answer to the gigs'

They flew an 11 box per side array of Silver boxes. with 4 stacks of cardioid subs - 3 high in each stack (1 each side of silver boxes in a subs, silver boxes, subs config ) No infills.

 

Bare in mind at this point, its a venue of short - medium throw distance and the bottom of the line array was head height with a curve up covering the balcony.

 

the silver boxes are quoted as , " a system which is designed particularly for very high SPL requirements with great throw distances".

 

 

2. I noticed on the Smaart rig that was being used... 1 kHz was approximately 115dB - 120dB, 250Hz was approximately 96dB. (this was during a chorus of one particular song... which was actually a ballad). This was A weighted. So I understand that LF is 'rolled off', but at 250Hz (ish), the roll off is not that steep and also bear in mind the actual level at 1kHz considering the flecture Munson curves (someone will quote me for spelling on that one I'm sure)

 

What would the users of this forum consider to be 'acceptable' levels during these type of rock gigs - time is over approximately 2 hours 30 mins (2 support, one headline)?

 

 

3. When promoters put on the ticket something like, " customers must take responsibility for their attendance at the event with respect to understanding that their hearing will be subjected to high sound levels and it is the customers responsibility alone to accept these levels or dont come"

 

Should they be allowed access to recorded gig level material (such as a calibrated smaart log / norsonic log) to actually know what they have been exposed to.... bearing in mind SPL / Frequency / most sensitive areas of the human hearing system.

 

 

 

 

I ask this because as an engineer who's worked at that venue before and been around many professional and none professional acts, and also been a punter for numerous gigs over the course of my shortish life.... I've never experienced such a poor quality sounding event, and I've never experienced that level of 'Temporary Tinnitus' effects from that room ( nearly 2days later and still buzzing heavily) from any other system...ever. (and this was shared by another group in the audience, in which that group actually left half way through the event from the sound)

 

I also ask this because I'd like to generally understand what other system designers/ engineers out there consider to be an acceptable level / what their considerations to these mid sized venues would be in terms of their system design and deployment?

 

This is not a rant in anyway, I'm sure there was an explanation to their system design / gig / coverage (no infills, relied completely on the silver line array which was about 12-14 m apart).

 

I would just like to open up the discussion to how we on here might do the job, whilst considering providing good audience sound practically.

 

Many thanks ;)

 

Simon West

[Simon Lewis]

Simon,

 

Condensing the points a little...

 

What would you consider to be an appropriate system design for these venues?

 

I'd guess that the simple answer is whatever provides suitable coverage, clarity, sound pressure level and headroom to suit the genre played. However, the reason for a particular system being carried on a tour might not be fully tied in with such issues. Perhaps a particular system was being demoed, or some venues were larger/more problematic, or that the band had specified a high SPL system?

 

I noticed on the Smaart rig that was being used... 1 kHz was approximately 115dB - 120dB

 

Well, that's loud... presuming that Smaart was actually calibrated to a known SPL (not always that likely). Given the collective TTS, it doesn't look as if it was too far off.

 

When promoters put on the ticket something like, " customers must take responsibility for their attendance at the event with respect to understanding that their hearing will be subjected to high sound levels and it is the customers responsibility alone to accept these levels or dont come"

 

You could argue (given the ticket warning) for 'volenti non fit injuria' - the punters knew it would be loud and they consented to that. On the other hand, "the general requirements of the HaSaW act and civil law duties relating to negligence reveal that audiences need to be protected against and informed of the risk of damage to their hearing" (Event Safety Guide, 1999).

 

The ESG suggests audience exposure is limited to an event LEq of 107db(A), so you'd be looking for (say) and eighth of the overall exposure time at 116dB(A) (about 18 minutes!).

 

If the gig was "silly loud" or caused actual damage, then court cases have been bought successfully before now. I don't know if a venue will readily let you look at any noise logs, but a number do keep them for fear of litigation. Have you contacted the venue/promoter/band/council etc.?

 

I could not accept that printing a warning absolves the engineer etc. from responsibility. We're not talking CoNaW regs here, but whether it is an act of negligence to run a high SPL system close to people ears when it reads 120dB at FOH. Some will argue, "it's art" others will smell a tort! It's something of a can of worms...

[greenalien]

This sort of thing is a perpetual beef of mine - I think that there are too many sound 'engineers' around who have damaged hearing, and turn up their rigs to compensate.

High-frequency hearing response also falls off naturally with age, so the older the engineer, the more 'top' is likely to be in the mix.

So - should hearing tests be compulsory for sound engineers? Discuss!

[Shaggy]

I recently saw a band at a similar sized venue playing with quite loud and not particularly good sound coming through silver boxes. However, while I am sure that it is possible to get a nice sound from the stage to the audience ears it's still possible that overly loud stage volume could have played a part, or the bands manager could be micromanaging the sound in a bad way or any one of a number of ways that will mess with the mix. Bearing in mind the band themselves are quite old and played rock and roll in less sophisticated days it's quite possible stage volume was very loud. It was a rock show and did need to be reasonably loud, otherwise plenty more people would complain. As someone who's seen plenty of gigs surely taking ear plugs would be the way to go?

 

It's easy to say "I would have done it this way" but until you are actually setting up the system and dealing with the acoustic/human realities of the gig you never know how it can go wrong and if the problems presented can be solved. Despite the reasonably poor sound I saw what was one of the best gigs I have seen in a long time and did not have any problems the next day.

[Matt Riley]

I love it, just as I'm revising this area of tort law for my day job, Simon comes in with a bit of classic stuff on volenti non fit injuria!

 

I reckon that we'll struggle to ever end up with any litigation in this area, and I'll be stuck reading boring cases about local authority windows and medical negligence, but if, hypothetically, you could prove that the volume generated in this venue was not 'in accordance with a practice accepted as proper by a reasonable body of [sound] men skilled in that particular art', then I doubt the defence of volenti would stand, especially if, like in this case, the volume is far higher than could be reasonably assumed by the punter having attended similar events with this warning in the past, then I can see some significant vicarious liability claims under the tort of negligence.

 

Something to think about,

 

M

[Doug Siddons]

Just a quick question.. were the venue staff supplied with ear plugs?

[Bobbsy]

If those numbers are true, I'm surprised that most of the punters weren't crying out in pain! Hearing 1kHz at 120dB would not be pleasant and could certainly result in hearing damage very quickly.

 

However, a word of caution. I notice you say the measurements you saw were "A weighted" but then go on to talk about SPLs at specific frequencies. These statements aren't entirely compatible. An "A" weighted SPL would give you a single, averaged reading over the entire audible spectrum, weighted using, in effect, the reverse of the Fletcher-Munson curve for human hearing. This means that changes in the indicated SPL fairly closely match the perceived changes in level that you hear.

 

For this reason, I'm slightly sceptical of the numbers you quote. However, I'm fully with you on the general principle. Sound professionals have got to get away from the idea that "louder is better". Between live music and the insidious effect of ear buds and iPods, we're breeding a generation of young people with hearing difficulties. If you read up on some older threads, you'll see that the choice of SPL is being taken away from the performer and sound engineer and becoming subject to government legislation to protect people. Alas, some of the new rules are going to be pretty draconian.

 

As for the choice of boxes, I agree that the system you describe sounds unsuitable for the venue. However, what we don't know is if this was a touring act. If it was, it's often necessary to carry with you a system suitable for a "typical" venue and this is not always ideal for every place you visit.

 

Bob

[Simon Lewis]

However, a word of caution. I notice you say the measurements you saw were "A weighted" but then go on to talk about SPLs at specific frequencies. These statements aren't entirely compatible. An "A" weighted SPL would give you a single, averaged reading over the entire audible spectrum, weighted using, in effect, the reverse of the Fletcher-Munson curve for human hearing. This means that changes in the indicated SPL fairly closely match the perceived changes in level that you hear.

 

A small caveat, Bobbsy (treading carefully, so as not to challenge an acknowledged expert!)...

 

A weighting is based on the 40 phon Fletcher Munson curve, and therefore more closely mirrors the human perception of loudness at low sound pressure levels. At concert levels, Fletcher Munson shows a flat curve to about 3kHz, then a dip and then a rise at about 10kHz. The more recent ISO 226 curve does show a 10 to 20dB loss at bass frequencies for the 100phon contour. Consequently, the A weighted reading would underestimate noise exposure, since it filters out low frequencies and to a lesser extent, high frequencies. This is usually seen to be to our advantage as the EHO can't tell us off for a driving bass beat, if his SLM is set to A weighting! Also, if a spot frequency of 1kHz is measured, then it's the same value for A, B, C, D and Z weightings - one of the reasons why pistonphone calibrators use 1kHz.

 

I can't say how Smaart was set up at this gig, but it's possible to show the non weighted RTA and the A weighted single figure SPL on the same screen.

 

Simon

[simonwest]

Hi again

 

Thank you for your so far responses, It is all very interesting and relevant to our industry today

 

Let answer a few questions

 

However, what we don't know is if this was a touring act

 

In my previous post I mentioned that the act was on tour, however I did not make clear that this particular rig was on tour. It was througout the uk dates, and as mentioned was places like (but definately no bigger than!) Manchester apollo, Brixton Academy, Leeds univeristy and alike.

 

I completely understand that the smaart rig maybe un accurate / un calibrated (Simon Lewis has taught very well in 'interesting' lectures <_< )... I was attempting to show an example between the difference between two areas of the frequency spectrum with respect to the fletcher munson curve.... and how we as engineers decide what system we use, how we rig it, and how we mix within particular system restrictions. I cannot comment on the exact smaart settings because I didnt spend long enough looking at it (trying my best to enjoy the gig).

 

The gig overall, was really good... the lighting was very clever and the band performed excellent, and took the time too meet people after the gig (the missus was very happy with her picture and signature from many of them) after temporary threshold shift the sound was not 'as bad'.... my ears are still ringing though (the gig was monday) and with work to do this weekend with some rather loud bands.... I'll be keeping my plugs in

 

Many thanks for all replies so far

 

Simon West

[Bobbsy]

Simon Lewis: Thanks for the kind words and I completely agree with your caveats. I was trying to keep it simple in my previous post but this always leads to glossing over something. My main point was (as you said far better than me!) that, for spot readings, you will get the same number regardless of what weighting is set.

 

Simon West: I don't know any of the venues you mention so can't make a detailed comment on the suitability of the rig for any stages of the tour. However, it is very fair to say that any gig that leaves your ears ringing two days later was far too loud. Slightly OT, but in another forum I visit (not industry related) somebody posted a link to a "test your hearing" site. People have been posting what their results were...and surprisingly it's the old fogies like me who seem to have better hearing than the younger members. Between loud live events and the insidious danger of ear buds and iPods, we are raising a generation or two of people with hearing difficulties.

 

Bob

[mervaka]

on that topic, I see so many teenagers coming into my corner shop (dayjob) with ipods blaring at full blast. when I mention to them about how its damaging (and how I have tinnitus etc) they just laugh. such a shame/waste/etc. arrogance prevails.

[Shez]

Slightly OT, but in another forum I visit (not industry related) somebody posted a link to a "test your hearing" site.

 

Any chance you could post it here? I'm not sure how many people here would be willing to publicly share their results but it would certainly be interesting to see where one's own ears sit...

[simonwest]

Just a quick note..

 

Its now Friday morning and the ringing has gone...... longest temporary tinittus I've ever experienced.

 

I'd also be interested in the link to test your hearing at home, granted it should be used as a guideline only, but to give myself (and some people I know maybe) an idea of what their hearing is really like.... that would be good

 

Cheers

 

Simon

[Bobbsy]

I hesitated to post the link the folks on the other site were playing with because, frankly, it's not very good. However, if you want to have a play, the site is

HERE. The biggest problem is that the "test" goes up to frequencies well beyond the ability of most computer speakers or cheap headphones to reproduce properly...but the tones aren't filtered so you tend to get some rubbish at lower frequencies when you try to listen to the higher notes.

 

Just for fun, I did a google on "hearing test online" and came up with quite of few links, some of which may be better.

 

Frankly, I tend to generate my own using Audition though.

 

Bob

[p.k.roberts]

I've not found a decent online site, but I do own a copy of this CD;

 

http://digital-recordings.com/audiocd/audio.html

 

Whilst I'm not sure as to the value of the absolute measurements, I think it's useful for monitoring long term trends.